Automatic focusing camera with control of focusing optical system position and driving power source velocity

ABSTRACT

An automatic focusing camera system has a lens barrel with a focusing optical system, and a camera body. A focus detecting device in the camera body outputs a focus detecting signal. A calculating device in the camera body calculates driving information of the focusing optical system based upon the focus detecting signal. A driving device in the lens barrel has a driving power source and a transmission member for transmitting driving power to the focusing optical system to drive it based upon the driving information. First and second signal generators in the lens barrel, at respective final and initial stages of the transmission member, generate first and second driving signals in response to driving of the focusing optical system A driving control device in the lens barrel controls position of the focusing optical system based upon the first driving signal and the driving information, and controls velocity of the driving power source based upon the second driving signal.

This is a division of application Ser. No. 782,297 filed Oct. 24, 1991,now U.S. Pat. No. 5,250,976.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic focusing camera. Moreparticularly, the invention relates to a camera capable of performing ahighly precise focusing by providing detecting means on the lens sidefor detecting the driving amount of a focusing optical system.

2. Related Background Art

FIG. 12 illustrates an example of a conventional automatic focusingcamera. In the camera shown in FIG. 12, an exchangeable photographinglens 41 is mounted on the body 42, and an objective image passingthrough the photographing lens 41 is detected by a photoelectricconversion section 45 through a main mirror 43 and a sub-mirror 44. Theoutput from the photoelectric conversion section 45 is inputted into afocus detecting means through an A/D converter incorporated in amicrocomputer (hereinafter referred to as CPU) 50 to obtain a defocusamount. In the meantime, lens data per se is inputted into the body sidefrom the photographing lens 41 through lens data transmitting/receivingcontrollers 48 and 49 on the lens side and body side respectively, and acalculating means in the CPU 50 works out a required driving amount fora motor 52 on the basis of this lens data per se and the defocus amountobtained from the aforesaid detecting means 47. The deta indicating therequired driving amount is applied to one of the inputs of the incidencedetector in the CPU. To the other input of the aforesaid incidentdetector, signals corresponding to the driving amounts from aphotointerrupter 54 provided in the body 42 and a pulse counter 55 areinputted in order to obtain the signal which corresponds to the drivingamount of the motor 52. The coincidence detector compares this signalcorresponding to the driving amount and the signal corresponding to therequired driving amount obtained from the aforesaid calculating means.Thus, a signal corresponding to the difference between them isgenerated. The signal thus obtained is applied to the motor 52 through amotor driver 56. In this way, the motor 52 drives the focusing opticalsystem L2 in the photographing lens 41 side through a coupling member 57between the camera 42 and the lens 41 to perform focusing.

However, in the above-mentioned conventional camera, as the drivingamount of the focusing optical system L2 is obtained by the pulseobtainable from the photointerrupter 54 mounted on the motor drivingshaft, there have been encountered the problems given below.

(1) It takes a constant time before the defocus amount is obtained afterthe signal from the photoelectric conversion section 45 has beeninputted into the focus detecting means 47. If a focus detection isperformed while the focusing optical system L2 is being driven, theposition of the focusing optical system L2 is dislocated from a positionat which to begin obtaining the focus amount by a portion equivalent tosuch a constant time required for obtaining the defocus amount.Therefore, if the focusing optical system L2 is driven at it is from theresult of the focus detection, the focusing optical system L2 cannot bestopped at a position where the focusing optical system has come intofocus.

(2) Due to the mechanical gaps existing in the gears and others betweenthe motor driving shaft in the camera body 42 side and the focusingoptical system L2, the pulse numbers obtainable from thephotointerrupter 54 do not coincide with the actual position of thefocusing optical system L2 perfectly. Particularly, when driving pulsesare output to reverse the driving direction, there are some cases wherethe focusing optical system L2 is not driven because of the backlashesof the gear 15, coupling member 57, and the like. It is thereforenecessary to use a highly precise gear 15 and coupling member 57 forpositioning the focusing optical system L2.

(3) When the focusing optical system L2 should be driven for a preciseamount to be in focus in particular, it is preferable to drive the motorat a low speed for several pulses to enable the focusing optical systemL2 to be positioned accurately.

SUMMARY OF THE INVENTION

Therefore, in consideration of the problems existing in a cameraaccording to the conventional example set forth above, the objectives ofthe present inventions are:

(1) to provide an automatic focusing camera system wherein the positionof the focusing optical system is known whenever the focusing opticalsystem is being driven and the focusing optical system is driven to afocusing position by comparing the position of the focusing opticalsystem in motion and the defocus amount;

(2) to provide an automatic focusing camera system capable of performinga highly precise focusing without being affected by the mechanical gapsexisting between the motor driving shaft and the focusing opticalsystem;

(3) to provide an automatic focusing camera system capable of drivingthe motor at a low speed particularly when the focusing optical systemshould be driven for a precise amount to be in focus; and

(4) to provide as another objective a camera body capable of performingan optimal focusing for various types of photographing lenses in thecase where any one of the various types of photographing lensesincluding photographing lenses of conventional constructions is mountedthereto.

According to the present invention, it is possible:

(1) to drive the motor driving amount of the focusing optical system issmall and to drive the motor at a high speed when the driving amount ofthe focusing optical system is large;

(2) to grasp the position of the focusing optical system accurately evenwhen it is in motion by detecting the position of the focusing opticalsystem;

(3) to grasp the position of the focusing optical system accuratelybecause signal generating means is provided at the final stage to drivethe focusing optical system; and

(4) to enable also a photographing lens to be in focus by switchingsignals from signal generating means in the camera body even in a casewhere a conventional photographing lens, in which no signal generatingmeans is incorporated, is mounted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a lens barrel constitutinga first embodiment;

FIG. 2 and FIG. 3 are views illustrating schematically the structure ofsignal generating means;

FIG. 4 a view illustrating the converting process of the output signalsfrom a light receiving section;

FIG. 5 is a schematic block diagram showing a camera system according tothe first embodiment;

FIG. 6 is a flowchart illustrating the procedures for the positioncontrol and velocity control;

FIG. 7 is a schematic block diagram showing a second embodiment of thecamera system;

FIG. 8 is a schematic block diagram showing a third embodiment of thecamera system;

FIG. 9 is a schematic block diagram showing a forth embodiment of thecamera system;

FIG. 10 is a schematic block diagram showing a fifth embodiment of thecamera system;

FIGS. 11A and 11B are block diagrams showing the electrical contactconnecting the lens and camera body; and

FIG. 12 is a schematic block diagram illustrating a conventional exampleof a camera system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a cross-sectional view illustrating a lens barrel of a firstembodiment of a camera system according to the present invention.

The photographing system comprises three lens groups of L1, L2, and L3.The focusing optical system is designated by L2 and is supported by asupporting barrel 2.

The fixed barrel 1 is a member to fix the lens barrel to the camera bodyconstituting the embodiment, and the lens barrel is mounted on thecamera body by a bayonet nail 1a.

The fixed barrel 1 has its outer barrel 1b and inner barrel 1c, and tothe inner periphery of the inner barrel 1c, the photographing systems L1and L3 are fixingly supported while the focusing optical system L2supported by the supporting barrel 2 is slidably supported thereon. Inthe fixed barrel, a pin 5 is planted. The supporting barrel 2 supportsthe focusing optical system L2 and fits in the fixed barrel 1.

In the supporting barrel 2, a pin 3 is planted.

The pin 3 fits in a linear guide groove 1d provided in the inner barrel1c of the fixed barrel 1 and a lead groove 4a provided in a rotationalbarrel 4.

The rotational barrel 4 is rotatively fitted on the outer periphery ofthe inner barrel 1c of the fixed barrel 1. In the rotational barrel 4,the lead groove 4a and a circumferential groove 4b are cut.

The lead groove 4a is fitted for the pin 3 planted on the supportingbarrel 2 for supporting the focusing optical system L2 while thecircumferential groove 4b is fitted for the pin 5 planted on the fixedbarrel 1, and by the pin 5 the movement in the optical axis is regulatedand at the same time, the rotation around the optical axis is regulatedwith a predetermined angle.

At the end of the rotational barrel 4, a rotational section 6 isinstalled to rotate accompanying the rotation of the rotational barrel4. The rotational section 6 is a rotational section 120 shown in FIG. 2and FIG. 3 with a plurality of slits formed therein. Thephotointerrupter 7 comprises an index scale 123, light emitting section121, and light receiving section 122 shown in FIG. 2 and FIG. 3. In thisrespect, electrical parts and others are stored at 7a.

The pin 5 is planted on the fixed barrel 1 to fit into thecircumferential groove 4b of the rotational barrel 4 to regulate themovement of the rotational barrel 4.

A solenoid 8 is of a bistable type and is planted on the outer peripheryof the rotational barrel 4. Its axis 8a is provided movably forward andbackward in the axial direction by electric signals from a switch (notshown).

A distance operation ring 13 is a barrel in order to perform focusingmanually. In the distance operation ring 13, a projecting section 13a isprovided on its inner side projectingly in front of the shaft 8a of thesolenoid 8. Along its circumferential direction, a plurality ofelongated holes 13b are provided coaxially with the shaft 8a to fit forthe shaft 8a. These holes are arranged so that one of the elongatedholes 13b is fitted for the shaft 8a when the shaft is at its front sideposition in a so-called manual focusing state and is not fitted for theshaft when it is at its rear side position.

A segment gear 14 is a driving force transmission member for thefocusing by an automatic operation. In the segment gear 14, a projectionsection 14a is projectingly provided in the rear side of the shaft 8a ofthe solenoid 8. Along its circumferential direction, a plurality ofelongated holes 14b are provided coaxially with the shaft 8a to fit forthe shaft 8a. These holes are arranged so that one of the elongatedholes 14b is fitted for the shaft 8a when the shaft is at its rear sideposition in a so-called automatic focusing state and is not fitted forthe shaft when it is at its front side position.

The motor 15 is fixed to the fixed barrel 1 and its driving force istransmitted to the segment gear 14 through a gear 16, gear 21, and gear17 which form a speed reduction gear train.

With the gear 16 mounted on the shaft of the motor 15, the gear 18engages, and to the gear 18, a disc type rotational section 19 is fixed.On the rotational section 19, a plurality of slots are formed radiallyfrom its axial center. A photointerrupter 20 is the same as shown in theaforesaid FIG. 2.

Now, the operation of the photographing lens in the first embodimentwill be described.

When the autofocusing mode for the automatic focusing operation isselected by changing a mode switch (not shown), this selection signal isinputted into a CPU 100 shown in FIG. 5. Then, this signal causes themotor 15 fixed to the fixed barrel 1 to be rotated through the CPU 100and the motor driver 15a, and its driving force is transmitted to thesegment gear 14 through the gear 14, gear 21 and gear 17 constitutingthe speed reduction gear train. Thus, one of the elongated holes 14bprovided along the circumferential direction of the projection 14a ofthe segment gear 14 fits the shaft 8a of the solenoid 8 which is movedbackwards by the AF mode switching.

As the solenoid 8 is fixingly provided on the outer peripheral side ofthe rotational barrel 4, the rotation of the motor 15 is transmitted tothe rotational barrel 4 through the segment gear 14 to rotate therotational barrel 4. When the rotational barrel 4 is rotated, thesupporting barrel 2 is moved along the lead groove 4a in the directionof the optical axis, so that the focusing optical system L2 is driven inthe driection of the optical axis to be in focus.

Now, by switching the mode switch to select the manual focusing mode forthe manual focusing operation so that the distance operation ring 13 canbe operated manually. Then, one of the elongated holes 13b providedalong the circumferential direction of the projection 13a of thedistance operation ring 13 fits the shaft 8a of the solenoid 8 which hasmoved forwards by the switching to the manual focusing mode. As thesolenoid 8 is fixingly provided on the outer peripheral side of therotational barrel 4, the rotation of the distance operation ring 13 istransmitted to the rotational barrel 4 to rotate the rotational barrel4. Thereafter, the focusing operation system L2 is driven in thedirection of the optical axis to be in focus as in the case of theautomatic focusing operation.

Subsequently, referring to FIG. 2, FIG. 3, and FIG. 4, the descriptionwill be made of the structures of the rotational section andphotointerrupter which constitute signal generating means.

Sandwiching the rotational section 120 with a plurality of slits formedtherein, which rotates accompanying the rotation of the rotationalbarrel 4, the light emitting section 121 and two light receivingsections 122a and 122b are arranged. Between the rotational section 120and the two light receiving sections 122a and 122b, the index scale 123is fixingly arranged. The index scale 123 comprises as shown in FIG. 3slits 123a arranged in front of the light receiving section 122a and theslits 123b arranged in front of the light receiving section 122b, thephase of which is dislocated by a 1/4 phase with respect to the slits123a.

The reason why the index scale 123 is structured in this way is that notonly the variable amount of the position of the focusing optical systemL2 but the moving direction of the focusing optical system L2 can alsobe detected.

Light emitted from the light emitting section 121 reaches the lightreceiving section 122a whenever the slits of the rotational section 120and the slits 123a of the index scale are in the relationship ofoverlapping each other even slightly. An output waveform is output asshown in FIG. 4 (a-1), which is converted into a pulse signal as shownin FIG. 4 (a-2) by electrical processing. Likewise, light emitted fromthe light emitting section 121 reaches the light receiving section 122bwhenever the slits of the rotational section 120 and the slits 123b ofthe index scale are in the relationship of overlapping each other evenslightly. An output waveform is output as shown in FIG. 4 (b-1), whichis converted into a pulse signal as shown in FIG. 4 (b-2) by electricalprocessing. The phase of the pulse signal generated in the lightreceiving section 122b is dislocated by a 1/4 cycle as compared withthat of the pulse signal generated in the light receiving section 122a.At this time, the rotational direction of the rotation of the rotationalsection 120 is detected on the basis of the output timings of the lightreceiving sections 122a and 122b, and using two signal lines therotational direction is transmitted to the CPU 109 in the body togetherwith the rotational extent of the rotational section 120. Thesynthesized pulse signals to be transmitted are such as shown in FIG. 4(a-3) and FIG. 4 (b-3).

Also, the structure may be arranged so as to output the two pulsesignals shown in FIG. 4 (a-2) and FIG. 4 (b-2) to the two signal lines.

Now, the description will be made of a camera system according to thefirst embodiment wherein an exchangeable photographing lens is mountedon the camera body.

FIG. 5 illustrates the fundamental structure of an automatic focusingcamera system according to the first embodiment.

The camera body 10a has a semi-transparent mirror 43, total reflectionsub-mirror 44, photoelectric conversion section 45, CPU 101, and lensdata transmitting/receiving controller 33.

Also, a lens data transmitting/receiving controller 34 is provided inthe lens 1a in order to transmit or receive electric signals between thephotographing lens 1a and camera body 10a, and the structure is arrangedso that communications are possible through the lens contact 35. Also,the source power V_(cc) for operating a CPU 100, lens datatransmitting/receiving controller 34, and others is supplied from thecamera body 10a side through the lens contact 36.

The light beam from an object reaches the main mirror 43 of the camerabody 10a through the photographing lens 1a, and a part of the light beamwhich has passed the main mirror 43 is reflected by the sub-mirror 44 tobe induced into the photoelectric conversion section 45. Thephotoconversion section 45 is a line sensor comprising a semiconductorCCD element, for example.

The output signal from this photoelectric conversion section 45 isinputted into the CPU 101 in the camera body. In the CPU 101, the outputsignal is converted from analog signal to digital signal by the A/Dconverter and is inputted into the focus detecting means.

In this respect, while a focus detecting method of the so-called passivetype is illustrated in FIG. 5 and FIG. 7 to FIG. 10, it may be possibleto employ a detecting method of the active method for the purpose.

The aforesaid focus detecting means obtains a defocus amount by theknown technique. The calculating means receives through the lens datatransmitting/receiving controller 33 the lens data per se which has beentransmitted from the lens 1 through the CPU 100 in the lens side and thelens data transmitting/receiving controller 34, and works out the pulsemembers corresponding to the required driving amount using this lensdata per se and the aforesaid defocus amount. In other words, the lensdata per se which has been transmitted from the lens side includesmonitor pulse numbers Plns per driving amount for a unit image area, forexample. Therefore, given a defocus amount obtained by the aforesaidfocus detecting means as Df, the driving pulse members required forfocusing, i.e., the required driving pulse numbers N are obtained in theexpression given below.

    Df×Plns.

On the other hand, the photointerrupter 7 on the lens side outputspulses in accordance with the driving of the supporting barrel 2, andthe pulses are inputted into the pulse counter 32 in the photographinglens. The pulse counter 32 counts the pulses to input them into an inputof the coincidence detecting means in the CPU 100. To the other input ofthe coincidence detecting means, the required driving pulse numbers N,which have been transmitted from the CPU 101 to the CPU 100, areinputted. The driving control means continues transmitting the drivingsignals to the motor driver 15a for driving in the focusing directionwith respect to the detected defocus state until both of the inputtedpulse numbers coincide. Hence, the motor 15 is driven, and the rotationof the aforesaid motor 15 is transmitted to the gears 14, 16, and 17,and others in the lens to drive the supporting barrel 2 in the directionof the optical axis. Then, at this juncture, the output pulse numbersfrom the photointerrupter 7 are inputted into the pulse counter 32simultaneously.

In this way, the motor 15 is driven to move the focusing optical systemL2, and when the required driving pulse numbers N obtained by theaforesaid calculating means and the output of the pulse counter 32coincide, the coincidence detecting means detects this, and on the basisof this detection, the driving control means stops the driving signaltransmission to the motor driver 15a to terminate the driving. Thus, thefocusing is completed.

To drive the focusing optical system L2, the driving velocity should becontrolled. In a case where the velocity control is performed by a knowntechnique, it is necessary to provide a feedback signal for return. Itmay be possible to use the output pulse of the photointerrupter 7 as afeedback signal or a motor shaft photointerrupter 20 instead of thephotointerrupter 7.

The perform the velocity control of the motor using the motor shaftphotointerrupter 20 by detecting the position of the focusing opticalsystem L2 by the photointerrupter 7 makes it possible to secure theprecision for the positional detection of the focusing optical system L2as well as to perform an accurate control because the rotational speedof the motor can be detected accurately.

Here, in this case, it may be possible to use a motor shaftphotointerrupter 20 which is capable of detecting the rotational amountonly. This is because the motor shaft photointerrupter 20 is onlyrequired to perform the velocity control, and it is unnecessary for thisphotointerrupter to detect the driving direction of the focus opticalsystem L2.

Now, using a flowchart shown in FIG. 6 the description will be made ofthe operations of the positional control and velocity control by the useof the photointerrupter 7 and the motor shaft photointerrupter 20.

In step S1, the data for the defocus amount is received from the focusdetecting means and in the subsequent step S2, the lens driving amountfor the focusing optical system L2 is calculated on the basis of thisdefocus amount. Further in step S3, when the focusing optical system L2has been driven for the driving amount worked out in the above-mentionedstep, the total number of the pulses generated by the photointerrupter,i.e., the pulse numbers N corresponding to the driving amount, iscalculated. Subsequently, in step S4, whether the driving amount workedout in the step S2 exceeds a predetermined value A or not isdiscriminated, and if the amount exceeds the predetermined value A, thenthe process proceeds to step S10 or otherwise to step S5. Thispredetermined value A is a threshold value to be used for the selectionof the photointerrupter 7 with respect to the driving amount of thefocusing optical system L2 or the motor shaft photointerrupter 20.

In step S4, if the driving amount is discriminated to be less than thepredetermined value A, i.e., the focusing optical system L2 should bedriven finely, a low-speed instruction signal is given to the drivingcontrol means in step S5, and this low-speed instruction signal and thepulse signal from the motor shaft photointerrupter 20 are compared toperform a velocity feedback control so that the velocity of the motor 15becomes identical to the velocity of the low-speed instruction. Morespecifically, the pulse intervals of the pulse signal from the motorshaft photointerrupter 20 are detected to perform the driving control byrepeating the turn off and on of the motor 15 so as to define the timeintervals to be identical to the pulse intervals of the low-speedinstruction signal. At this juncture, due to the backlashes of the gearsin the lens driving mechanism, the actuation of the focusing opticalsystem L2 is delayed from the starting of the motor 15. In thesubsequent step S6, whether the pulse for the photointerrupter 7 isgenerated or not is discriminated, and if the pulse is generated, theprocess proceeds to step S7 or otherwise, returns to the step S5 tocontinue the low-speed control of the motor 15 in accordance with thefeedback signals from the photointerrupter 20.

If the photointerrupter 7 generates pulses, the pulses are counted instep S7, and the process advances to step S8. In the step S8, thecoincidence detecting means examines whether or not the counting valueof the generated pulses by the photointerrupter 7 is a pulse numbercorresponding to the driving amount worked out in the step S3, and ifthe counting value is found to have reached the pulse number correspondto the driving amount, then the process proceeds to step S9 to stop themotor 15 through the driving control means or otherwise, returns to thestep S7 to continue counting the pulse numbers.

If an affirmative result is obtained in step S4, then the motor 15 isactuated in step S10 to perform a high-speed driving control inaccordance with the feedback pulse signal from the photointerrupter 7.At this juncture, due to the backlashes of the gears in the lens drivingmechanism, the pulse generation of the photointerrupter 7 is lagged fromthe starting of the motor 15. Accordingly, there is a slight instabilityat the time to actuate the motor 15. However, as compared with theabove-mentioned operation for the fine driving amount, this time lag isextremely small and is negligible.

With the completion of the above-mentioned processing, the execution ofthe program is terminated.

In order to eliminate any errors in the positional control of thefocusing optical system L2 due to the backlashes in the lens drivingmechanism such as mentioned above, the photointerrupter 7 whichgenerates pulses in response to the driving amount of the focusingoptical system L2 and the motor shaft photointerrupter 20 whichgenerates pulses in response to the rotation of the motor are providedto control the velocity of the motor 15 at a low speed with the pulsesgenerated by the motor shaft photointerrupter 20 before the pulses aregenerated by the photointerrupter 7 when the driving amount of thefocusing optical system L2 is small and to count the pulses when thepulses are generated by the photointerrupter 7 for controlling thedriving amount of the focusing optical system L2. Hence, the motorvelocity is stabilized so as to stop the motor at an objective positionaccurately thereby to improve the precision of the focusing.

A second embodiment shown in FIG. 7 is a camera system wherein anelectric contact 31 is added to the photographing lens 1b and the camerabody 10b of the first embodiment.

In other words, the camera system according to the second embodimentenables the output of the photointerrupter 7 to be transmitted to theCPU 101 in the camera body 10b on real time through the electric contact31.

When a focus detecting is performed while the focusing optical system L2is in motion, the focusing optical system L2 is in an advanced positionby an amount (ΔN) which is a portion equivalent to a time (Δt) from thestart of photoelectric conversion in the photoelectric conversionsection 45 to the completion of the defocus amount calculation.

Therefore, if the required driving pulse numbers N obtained as above aregiven to the motor 15 as they are, the result is that the focusingoptical system L2 has eventually advanced from its proper focusingposition by an amount (ΔN).

Then, in the CPU 101 in the camera body side, the output pulses of thephotointerrupter 7, which are being transmitted from the lens 1b throughthe electric contact 31, are counted to measure the driving amount (ΔN)of the focusing optical system L2 on real tie for the duration of a time(Δt). Therefore, the required driving pulse numbers N1 are obtainable byan equation given below.

    N1=N-ΔN

To the motor the required driving pulse numbers N1 are given through thedriving control means, and the amount of the focusing optical system L2to be driven by this driving is inputted to the pulse counter 32, andthen is inputted into the CPU 100 in the lens side. The coincidencedetecting means in the CPU 100 detects the coincidence of the requireddriving pulse numbers N1 and the pulse numbers inputted into the pulsecounter 32 thereby to stop the driving and terminate the focusingoperation.

Hence, the output of the photointerrupter 7 is being transmitted to thecalculating means on real time to make it possible to drive the focusingoptical system L2 to an accurate focusing position even when thefocusing optical system L2 is in motion.

Now, a camera system according to a third embodiment will be described.

FIG. 8 illustrates the fundamental structure of an automatic focusingcamera system according to the third embodiment.

What differs in the present embodiment from the first or the secondembodiment is that while a motor is incorporated in the camera body 10c,the coupling members 37 and 38 for transmitting the driving power of themotor are respectively arranged in the photographing lens 1c and camerabody 10c.

As in the case of the first embodiment, the defocus amount of an objectis obtained by the functions of the photoelectric conversion section 45and focus detecting means. Also, the lens data per se is transmittedfrom the photographing lens side to enable the required driving pulsenumbers N to be obtained for the driving of the motor 115. The drivingcontrol means transmits the pulse numbers N to the motor driver 115a todrive the motor 115 in the camera body. The motor 115 drives the gearsin the camera body and coupling means 37 in the body side. As thecoupling means 37 on the body side is coupled to a coupling means 38 onthe lens side in the photographing lens, the driving power of the motor115 is also transmitted to the gears and others in the photographinglens. Thus, the focusing optical system L2 is driven.

In the meantime, driving pulses are generated from the photointerrupter7 in the photographing lens 1c as the focusing optical system L2 isbeing driven and are directly transmitted to the CPU 101 from the pulsecounter 132 in the camera body 10c. Hence, these driving pulses arecompared with the required driving pulse numbers by the coincidencedetecting means in the CPU 101.

When the motor 115 in the camera body is used, not only the backlashesof the gears but the mechanical gap is generated in the coupling portionof both of the coupling means 37 and 38. Therefore, it is difficult forthe conventional method to perform driving to obtain an accuratefocusing position.

With the present embodiment, however, the driving of the focusingoptical system L2 is detected at the rotational section 4 which drivesthe focusing optical system L2 finally, thus making possible the drivingthereof to an accurate focusing position.

Furthermore, the output of the photointerrupter 7 is also transmitted tothe camera body through the electric contact 31. Accordingly, it ispossible to grasp the accurate position of the focusing optical systemL2 even when the system L2 is in motion.

Subsequently, a camera system according to a fourth embodiment will bedescribed.

FIG. 9 illustrates the fundamental structure of an automatic focusingcamera system according to the fourth embodiment.

What differs in the present embodiment from the third embodiment is thata photointerrupter 120 is provided in the vicinity of a motor shaft. Inother words, the difference is that the motor and the motor shaftphotointerrupter provided for the second embodiment is now transferredfrom the inside of the photographing lens to the inside of the camerabody.

Therefore, even when the motor 115 is in the camera body 10d, it ispossible to perform an accurate positioning of the focusing opticalsystem L2 as well as an accurate velocity control of the motor 115. Inthis case, it is unnecessary to provide the motor 115 and motor shaftphotointerrupter 120 for everyone of the photographing lenses, enablingthe exchangeable lens to be manufactured at a lower cost.

In this respect, the description has been made of a camera systemwherein the photographing lens is detachably mounted to the camera body,but the present invention is also applicable to a camera system of alens shutter type.

Now, FIG. 10 is a schematic view showing an automatic focusing camerasystem according to a fifth embodiment of the present invention. Thebody 10e of the camera shown in FIG. 10 is structured to be able toselect the use of monitoring methods for the driving amount of the lensoptical system in accordance with the kinds of the lenses to be mounted.In other words, the body 10e of the camera shown in FIG. 10 is providedwith a selection circuit having NAND gates 60 and 61 capable ofexecuting wired OR, which is added to the structure of the body 10dshown in FIG. 9.

In a case where the lens 1c in which a photointerrupter for monitoringdriving amounts is incorporated is mounted to a camera body 10e such asthis, the CPU 101 recognizes that the lens has aforesaidphotointerrupter 7 therein on the basis of the lens data per se which isbeing transmitted from the lens side, and causes the output connected tothe NAND gates 60 and 61 to be at a high level, so that the output ofthe NAND gate 61, i.e., the pulse signal from the photointerrupter 7 inthe lens side, is applied to the pulse counter 132. In this case, theoutput from the NAND gate 60 is blocked. As a result, monitor pulsesbeing transmitted from the photointerrupter 7 in the lens 1c side areinputted into the CPU 101 to allow the focusing performance to becarried out in the same manner as in the case shown in the aforesaidFIG. 9.

On the other hand, in a case where the lens without a photointerrupterincorporated is mounted, the CPU 101 recognizes by the communicationwith the lens that there is no photointerrupter 7 incorporated in thelens side to cause the output connected to the NAND gates 60 and 61 tobe at a low level. Thus, the monitor pulses of the photointerrupter 120in the body side is inputted into the pulse counter in the CPU 101through the NAND gate 60. The output form the NAND gate 61 is blocked.Consequently, in this case, the monitoring pulses of the driving amountof the motor 115 detected by the photointerrupter 120 in the body sideare counted by the pulse counter, and on the basis of the counted value,the focusing is performed. Therefore, the camera body 10e shown in FIG.10 is capable of performing an automatic focusing appropriatelyirrespective of the types of the lenses mounted thereto.

Now, in a camera such as shown in FIG. 7 through FIG. 10, a contactingpin is provided as a lens contact in the vicinity of the lens mount forperforming the transmitting/receiving of electric signals between thecamera body and lens. However, as the number of the contacting pins arelimited, it may be possible to consider combining the uses of onecontacting pin and another. FIGS. 11A and 11B shows a case in which acontacting pin for communicating the handshake signal line H/S2 of ateleconverter lens, for example, used also as the contacting pin forcommunicating the output signals of the photointerrupter 7 provided inthe lens side.

FIG. 11A illustrates the connection of the lens contact when ateleconverter lens is mounted, for example, and there is no circuitprovided in the teleconverter side for receiving/transmitting thehandshake signal H/S1 but a transmitting/receiving circuit for anotherhandshake signal H/S2. A teleconverter lens such as this does not haveany photointerrupter. Accordingly, the contact 31 is dedicated for theuse of transmitting/receiving the handshake signal H/S2 for thecommunication between the teleconverter and body.

FIG. 11B, on the contrary, illustrates state where a lens having aphotointerrupter 7 in the lens side is mounted. In this case, thecontact 31 is used only for transmitting the output signals of thephotointerrupter 7 in the lens side. The handshake signal H/S2 is notused because the signal line for the H/S1 is used for the handshakesignal needed for the communication between the lens side and body side.

In this way, using another contact pin also as the contacting pin fortransmitting the signals from the photointerrupter in the lens side in acamera according to the present invention, it is possible to implement acamera capable of performing a highly precise focusing without providingany special contact pin for the purpose.

What is claimed is:
 1. An automatic focusing camera system provided witha lens barrel in which a focusing optical system is incorporated, and acamera body, comprising:driving means incorporated in said lens barrel,said driving means having a driving power source and transmission memberfor transmitting the driving power of said driving power source to saidfocusing optical system; first signal generating means incorporated insaid lens barrel, said first signal generating means being provided atthe final stage of said transmission member to generate a first drivingsignal in response to the driving of said focusing optical system; firstterminal means provided in said lens barrel, said first terminal meanstransmitting said first driving signal to said camera body on real time;focus detecting means incorporated in said camera body, said focusdetecting means detecting the focusing condition of an objective imageto output focus detecting signal; second terminal means provided in saidcamera body, said second terminal means receiving said first drivingsignal on real time; and calculating means incorporated in said camerabody, said calculating means calculating the driving information of saidfocusing optical system on the basis of said focus detecting signal andsaid first driving signal.
 2. A camera system according to claim 1,whereinsaid system includes the following: driving control meansincorporated in said camera body, said driving control means controlsthe position of said focusing optical system and the velocity of saiddriving power source, based upon said driving signal and said drivinginformation.
 3. A camera system according to claim 1, whereinsaid systemincludes the following: second signal generating means incorporated insaid lens barrel, said second signal generating means being provided atthe initial stage of said transmission member to generate a seconddriving signal in response to the driving of said focusing opticalsystem; and driving control means incorporated in said lens barrel, saiddriving control means controls the position of said focusing opticalsystem based upon said first driving signal and said driving informationand controlling the velocity of said driving power source on the basisof said second driving signal.
 4. A lens barrel which is detachablymounted to a camera body having focus detecting means, and calculatingmeans for calculating driving information of a focusing optical systembased upon a focus detecting signal obtained by said focus detectingmeans, and in which said focusing optical system is incorporated,comprising:driving means, said driving means having a driving powersource, and a transmission member for transmitting driving power of saiddriving power source to drive said focusing optical system; first signalgenerating means, said first signal generating means being provided at afinal stage of said transmission member to generate a first drivingsignal in response to driving of said focusing optical system; secondsignal generating means, said second signal generating means beingprovided at an initial stage of said transmission member to generate asecond driving signal in response to driving of said driving powersource; and driving control means, said driving control meanscontrolling position of said focusing optical system based upon saidfirst driving signal and said driving information and controllingvelocity of said driving power source based upon said second drivingsignal; wherein said lens barrel further comprises terminal means, saidterminal means transmitting said first driving signal to saidcalculating means in real time.
 5. A lens barrel according to claim 4,whereinsaid driving control means controls the velocity of said drivingpower source in accordance with said second driving signal until saidfirst driving signal is output, and controls the velocity of saiddriving power source and the position of focusing optical system inaccordance with said first driving signal after said first signal isoutput.